The hypothesis tested in these studies was that prosthetic grafts of specific diamaters, biomaterial composition, and lumenal topography have different long term patency rates when used as brachiocephalic to pulmonary artery conduts. The specific aims were to test various types of grafts made from knitted and woven polyster (with and without internal/external velour), microporous expanded polytetrafluroethylene (EPTFE), bovine pericardium or ubilical vein. Fifth-four rhesus monkeys had a left thoracotomy and various grafts (4, 5, and 6 mm) with lengths of 2-5 cm inserted between the systematic and pulmonary circulations. There wre eight deaths prior to 3 month catheterzation. One monkey was unable to be catheterized secondary to poor vessels. Thirty of 45 grafts were patent at 3 months and 23 of 25 patent at 12 months. EPTFE showed a similar patency rate of 85% at 3 months and 12 months in 6 mm diameter prosthesis and 60% in the 4 mm size. Other materials were less satisfactory. These data suggest that when prosthetic conduits are used for palliation of pulmonary oligemia in infants and young children, the choice of conduit is highly important for long-term palliation. Further, prosthetic materials do not provide the long lasting palliation of the native sublavian artery as described in 1948 by Blalock and Taussig. Of the prosthetic materials available, EPTFE has the most consistent patency rates in 4 and 6 mm sizes. Patency rate is influenced by prosthesis diameter.